Reviewer 1:
(1) I think the proposed method imposes following additional prior: the
display surface must have salient black edges around the white screen. If so,
it should be added.
Answer: We mentioned this constraint in the Abstract.
(2) It is hard for me to understand the idea described in Section 6.2.2. Why
does a small third eigenvalue of the matrix indicate a degenerate case? Why
does a high forth eigenvalue indicate a large fitting error? This section has
to explain more in detail about the idea.
Answer: We added more details to this section.
(3) Figures are printed far from the place where they are referred.
Furthermore, Figures 9, 10, 11, 12, and 13 are referred to before the paper
refer to Fig.8. This makes the paper hard to understand particularly when it
is read with computer monitor as an electronic version. They should be reorganized well.
Answer: We corrected the order of the figures and changed the placement to
keep them closer to their references.
(4) Some figure numbers are not printed on the manuscript in section 6.
Please fill them.
Answer: Corrected.
Reviewer 2:
Nevertheless, parts of this work are overlapped or extended from authors’
previous work [21], e.g. Fig 8 and Fig 13 in [21], subsection 3.1.1 in both
manuscripts are similar. These identical points should be indicated with
citation. Authors can also explicitly explain resemblances and differences of
these two works in Section discussion.
Answer: We extended the related work section to further note the similarities
with [21]. We also added proper citations of [21] whenever the results are
borrowed from this work.
Besides, several minor defects need to be revised for publication:
1. Section 1 (Page2): the description of [27] (Brown et al.) and the
reference (Yang et al.) are inconsistent.
2. Subsection 3.1.1: the description of display coordinates and Fig.4 are
inconsistent.
3. Fig. 7: Left and Right should be revised as Top and Bottom.
4. Locations of figures should be close to their descriptions in the article.
For instance, Fig.5 should be close to subsection 3.2.1.
5. Figures about planar CAVEs are missed. E.g. the last line of Page9;
“Figures” in Section 6.
Answer: We applied all the corrections.
Reviewer 3:
given the tolerances that the technique is robust for with 2 pixel shifts one
need note that in the paper, as often such tolerance might be difficult to
achieve in some cases, whereby the technique woudl have to be modified a bit
to accomodate such differences, perhaps with a iterative feedback loop :) But
that is a topic for another paper.
Answer: We agree that for severe deviation from an extruded surface the
misregistration can become unacceptable. However, using a feedback loop will
result in non-interactive frame rate. Instead, our previous work [21] can be
used whenever interactive frame rate is not required and the surface deviates
severely from an extruded surface. We used a set of rational Bezier patches
in that work to avoid pixel misregistrations.
2ndly extracting exif focal lengths something that someitimes is inaccurate.
Answer: Fortunately, after dimension reduction our method does not need an
accurate estimation of the focal length as pointed in Section 3.1.3.
Lastly I suggest the autheros consider redoing thier pictures to not have
obvious blending issues. It doesn't look good, and makes it seems like the
authors techniques are less then they are. Especailly given that the authors
have solutions to those problems.
Answer: We agree that a better blending will improve the visual plausibility
of the results. But, unfortunately, we no longer have the flexible screen,
used in this work, to redo the experiments.
Reviewer 4:
The single camera registration is optimal for slight deformations in large
projection surfaces. The real challenge would potentially appear when
deformations become sufficiently severe to cause occlusions or multiple
tangent points with respect to the registration camera and the projector
geometry, Figure 4. Perhaps the authors would like to point out some
limitations in this respect.
Answer: We pointed in the introduction Section that our method assumes the
boundary of the display is visible from the camera viewpoint.
The dimension reduction effect on registration time, Table 1, is impressive.
However, it would be more clear if the authors also specify the actual setup
for the number given before and after dimension reduction.
Answer: We tried several display shapes in simulation and the reported time
is just for reconstruction of the display shape and does not include the
projector calibration. Therefore we did not mention the number of projectors.
We clarified it in the paper.
In some critial parts of the paper it would help if the authors keep the
proze linear and shorter as in the following suggestions.
Some suggetions:
Page 1, Section 1.1: Contributions:
“This is achieved by imposing two priors: (a) the display is a vertically
extruded surface; and (b) the aspect ratio of the planar rectangle formed by
the four corners of the display is known. We recover the camera and
projectors placement in two steps:
With these priors, we can use a single image of the piecewise smooth
vertically extruded surface to recover the camera pose and orientation and
the 3D display geometry via a non-linear optimization. To achieve fast
convergence and robustness of this step we propose a novel technique to
reduce the dimension of the higher dimensional space the non-linear
optimization have to operate on.
Next, we design a deterministic geometric algorithm which uses these
recovered properties to auto-calibrate (i.e. find both the intrinsic and
extrinsic parameters) each projector from a single pattern captured by the
camera.”
The contribution part can be improved by making the points shorter and
simpler. The priors, for example, (a) and (b) in the first paragraph are
again referenced in the first contribution. This is unnecessary. The
sentence: “To achieve fast convergence and robustness of this step we propose
a novel technique to reduce the dimension of the higher dimensional space the
non-linear optimization have to operate on.” Is not a contribution. It is an
evaluation of the method. The authors could simple use a shorter paragraph
that is closer to the technical details of the contribution.
The second point, “design a deterministic geometric algorithm” is not a
contribution. It is a very generic description that fits any technical paper.
Answer: Addressed in the Main Contributions section as suggested by the reviewer.